ADS8383 SLAS005B – DECEMBER 2002 – REVISED MAY 2003 18-BIT, 500-kHz, UNIPOLAR INPUT, MICROPOWER SAMPLING ANALOG-TO-DIGITAL CONVERTER WITH PARALLEL INTERFACE FEATURES D Zero Latency APPLICATIONS D Medical Instruments D Optical Networking D Transducer Interface D High Accuracy Data Acquisition Systems D Magnetometers D Low Power: 110 mW at 500 kHz DESCRIPTION D 500-kHz Sample Rate D 18-Bit NMC Ensured Over Temperature D Unipolar Input Range The ADS8383 is an 18-bit, 500 kHz A/D converter. The device includes a 18-bit capacitor-based SAR A/D converter with inherent sample and hold. The ADS8383 offers a full 18-bit interface, a 16-bit option where data is read using two read cycles or an 8-bit bus option using three read cycles. D Onboard Reference Buffer D High-Speed Parallel Interface D Wide Digital Supply D 8-/16-/18-Bit Bus Transfer The ADS8383 is available in a 48-lead TQFP package and is characterized over the industrial –40°C to 85°C temperature range. D 48-Pin TQFP Package BUS 18/16 SAR +IN –IN + _ Output Latches and 3-State Drivers CDAC BYTE 18-/16-/8-Bit Parallel DATA Output Bus Comparator REFIN Clock Conversion and Control Logic CONVST BUSY CS RD Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright 2002–2003, Texas Instruments Incorporated ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. ORDERING INFORMATION MODEL MAXIMUM INTEGRAL LINEARITY (LSB) ADS8383I ADS8383IB MAXIMUM DIFFERENTIAL LINEARITY (LSB) ±10 ±7 –2~7 2 7 –1~2.5 1 25 NO MISSING CODES RESOLUTION (BIT) PACKAGE TYPE 17 48 Pin TQFP 18 48 Pin TQFP PACKAGE DESIGNATOR TEMPERATURE RANGE PFB –40 C to –40°C 85°C PFB –40 C to –40°C 85°C ORDERING INFORMATION TRANSPORT MEDIA QUANTITY ADS8383IPFBT Tape and reel 250 ADS8383IPFBR Tape and reel 1000 ADS8383IBPFBT Tape and reel 250 ADS8383IBPFBR Tape and reel 1000 NOTE: For the most current specifications and package information, refer to our website at www.ti.com. ABSOLUTE MAXIMUM RATINGS over operating free-air temperature range unless otherwise noted(1) UNIT +IN to AGND Voltage Voltage range +VA + 0.1 V –IN to AGND 0.5 V +VA to AGND –0.3 V to 7 V +VBD to BDGND –0.3 V to 7 V +VA to +VBD –0.3 V to 2.5 V Digital input voltage to BDGND –0.3 V to +VBD + 0.3 V Digital output voltage to BDGND –0.3 V to +VBD + 0.3 V Operating free-air temperature range, TA –40°C to 85°C Storage temperature range, Tstg –65°C to 150°C Junction temperature (TJ max) Power dissipation TQFP package θJA thermal impedance Vapor phase (60 sec) Lead temperature, temperature soldering Infrared (15 sec) 150°C (TJMax – TA)/θJA 86°C/W 215°C 220°C (1) Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. 2 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 SPECIFICATIONS TA = –40°C to 85°C, +VA = 5 V, +VBD = 3 V or 5 V, Vref = 4.096 V, fSAMPLE = 500 kHz (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT Analog Input Full-scale input voltage (see Note 1) +IN – –IN Absolute input voltage 0 +IN –0.2 –IN –0.2 Input capacitance Input leakage current Vref Vref + 0.2 0.2 V V 45 pF 1 nA 18 Bits System Performance Resolution No missing codes ADS8383I (+IN – –IN) < 0.5 FS 18 (+IN – –IN) ≥ 0.5 FS 17 ADS8383IB Integral linearity (see Notes 2 and 3) ADS8383I (+IN – –IN) < 0.125 FS –4 (+IN – –IN) < 0.5 FS –6 6 (+IN – –IN) ≥ 0.5 FS –10 10 ADS8383IB Differentiallinearity Differential linearity Offset error (see Note 4) ADS8383I –7 –2/3 –1 2 (+IN – –IN) < 0.5 FS –1 3 (+IN – –IN) ≥ 0.5 FS –2 7 –1 –1/1.4 2.5 ADS8383I –1 ±0.5 1 –0.75 ±0.25 0.75 ADS8383IB ADS8383IB Vref = 4.096 V Vref = 4.096 V –0.1 0.1 –0.06 At 3FFFFh output code LSB ((18 bit)) 7 (+IN – –IN) < 0.125 FS Noise Power supply rejection ratio 4 ADS8383IB ADS8383I Gain error (see Note 4) Bits 18 0.06 LSB (18 bit) mV %FS %FS 60 µV RMS 75 dB Sampling Dynamics Conversion time Acquisition time 1.5 Throughput rate Aperture delay µs µs 0.4 500 kHz 4 ns Aperture jitter 15 ps Step response 150 ns 150 ns Over voltage recovery (1) Ideal input span, does not include gain or offset error. (2) LSB means least significant bit (3) This is endpoint INL, not best fit. (4) Measured relative to an ideal full-scale input (+IN – –IN) of 4.096 V 3 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 SPECIFICATIONS (CONTINUED) TA = –40°C to 85°C, +VA = +5 V, +VBD = 3 V or 5 V, Vref = 4.096 V, fSAMPLE = 500 kHz (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT Dynamic Characteristics ADS8383I ADS8383IB –110 VIN = 4 Vpp at 1 kHz –112 VIN = 4 Vpp at 10 kHz –108 ADS8383I Total harmonic distortion (THD) ((see Note 1)) ADS8383IB –98 ADS8383I ADS8383IB –99 ADS8383I ADS8383IB –90 VIN = 4 Vpp at 100 kHz –91 ADS8383I ADS8383IB 87 VIN = 4 Vpp at 1 kHz 88 ADS8383I ADS8383IB Signal to noise ratio (SNR) (see Note 1) 87 VIN = 4 Vpp at 10 kHz 87 ADS8383I ADS8383IB 87 87 VIN = 4 Vpp at 100 kHz 87 ADS8383I ADS8383IB 86 VIN = 4 Vpp at 1 kHz 87 ADS8383I Signal to noise + distortion (SINAD) ((see Note 1)) ADS8383IB 86 VIN = 4 Vpp at 10 kHz 86 ADS8383I ADS8383IB 86 85 VIN = 4 Vpp at 100 kHz 85 ADS8383I ADS8383IB 110 VIN = 4 Vpp at 1 kHz 112 ADS8383I S urious free dynamic range (SFDR) Spurious ((see Note 1)) ADS8383IB 98 VIN = 4 Vpp at 10 kHz 108 ADS8383I ADS8383IB dB 98 VIN = 4 Vpp at 50 kHz 98 ADS8383I ADS8383IB dB 86 VIN = 4 Vpp at 50 kHz ADS8383I ADS8383IB dB 87 VIN = 4 Vpp at 50 kHz ADS8383I ADS8383IB dB –98 VIN = 4 Vpp at 50 kHz 90 VIN = 4 Vpp at 100 kHz 94 –3dB Small signal bandwidth 3 MHz Voltage Reference Input Reference voltage at REFIN, Vref 2.5 Reference resistance (see Note 2) Reference current drain 4.096 4.2 500 fs = 500 kHz V kΩ 1 mA Bias Input Bias input range 2 2.048 Bias input drift Bias input current, sink (1) Calculated on the first nine harmonics of the input frequency (2) Can vary ±20% 4 –150 –100 2.1 V ±5 %FS µA ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 SPECIFICATIONS (CONTINUED) TA = –40°C to 85°C, +VA = +5 V, +VBD = 3 V or 5 V, Vref = 4.096 V, fSAMPLE = 500 kHz (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT Digital Input/Output Logic family Logic level CMOS VIH VIL IIH = 5 µA IIL = 5 µA VOH VOL IOH = 2 TTL loads IOL = 2 TTL loads +VBD–1 +VBD + 0.3 0.8 –0.3 V +VBD – 0.6 0.4 Straight Binary Data format Power Supply Requirements Power supply voltage +VBD (see Notes 1 and 2) 2.95 +VA (see Note 2) 4.75 Supply current, 500-kHz sample rate (see Note 3) Power dissipation, 500-kHz sample rate (see Note 3) 3.3 5.25 V 5 5.25 22 26 mA V 110 130 mW 85 °C Temperature Range Operating free-air –40 (1) The difference between +VA and +VBD should be no less than 2.3 V, i.e. if +VA is 5.5 V, +VBD should be at least 2.95 V. (2) +VBD ≥ +VA – 2.3 V (3) This includes only +VA current. +VBD current is typical 1 mA with 5 pF load capacitance on all output pins. 5 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 TIMING CHARACTERISTICS All specifications typical at –40°C to 85°C, +VA = +VBD = 5 V (see Notes 1, 2, and 3) PARAMETER MIN TYP MAX 1.5 UNIT µs tCONV tACQ Conversion time Acquisition time 0.4 tpd1 tpd2 CONVST low to conversion started (BUSY high) 10 50 ns Propagation delay time, End of conversion to BUSY low 10 20 ns tw1 tsu1 Pulse duration, CONVST low 40 ns Setup time, CS low to CONVST low 20 ns tw2 Pulse duration, CONVST high 20 CONVST falling edge jitter tw3 tw4 th1 Pulse duration, BUSY signal low Min(tACQ) Pulse duration, BUSY signal high Hold time, First data bus data transition (RD low, or CS low for read cycle, or BYTE or BUS18/16 input changes) after CONVST low µs ns 10 ps 1 µs 1.52 µs 40 ns 0 ns 0 ns 50 ns td1 tsu2 Delay time, CS low to RD low tw5 ten Pulse duration, RD low time td2 td3 Delay time, data hold from RD high tw6 th2 RD high tpd4 td4 Propagation delay time, BUSY falling edge to next RD (or CS for read cycle) falling edge tsu3 th3 tdis Disable time, RD High (CS high for read cycle) to 3-stated data bus 20 ns td5 Delay time, BUSY low to MSB data valid 30 ns 20 µs Setup time, RD high to CS high Enable time, RD low (or CS low for read cycle) to data valid Delay time, BUS18/16 or BYTE rising edge or falling edge to data valid 20 5 10 ns 20 ns 20 ns 125 ns Max(td5) 0 ns Setup time, BYTE or BUS18/16 rising edge to RD falling edge 10 ns Hold time, BYTE or BUS18/16 falling edge to RD falling edge 10 Hold time, last RD (or CS for read cycle ) rising edge to CONVST falling edge Delay time, BYTE edge to BUS18/16 edge skew tsu4 Setup time, BYTE or BUS18/16 change before BUSY falling edge 10 (1) All input signals are specified with tr = tf = 5 ns (10% to 90% of +VBD) and timed from a voltage level of (VIL + VIH)/2. (2) See timing diagrams. (3) All timing are measured with 20 pF equivalent loads on all data bits and BUSY pins. 6 ns ns ns ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 TIMING CHARACTERISTICS All specifications typical at –40°C to 85°C, +VA = 5 V, +VBD = 3 V (see Notes 1, 2, and 3) PARAMETER MIN TYP MAX 1.5 UNIT µs tCONV tACQ Conversion time Acquisition time 0.4 tpd1 tpd2 CONVST low to conversion started (BUSY high) 10 50 ns Propagation delay time, end of conversion to BUSY low 10 20 ns tw1 tsu1 Pulse duration, CONVST low 40 ns Setup time, CS low to CONVST low 20 ns tw2 Pulse duration, CONVST high 20 CONVST falling edge jitter Min(tACQ) µs ns 10 ps 1 µs 1.52 µs tw3 tw4 Pulse duration, BUSY signal low th1 Hold time, first data bus transition (RD low, or CS low for read cycle, or BYTE or BUS 18/16 input changes) after CONVST low td1 tsu2 Delay time, CS low to RD low tw5 ten Pulse duration, RD low td2 td3 Delay time, data hold from RD high 10 Delay time, BUS18/16 or BYTE rising edge or falling edge to data valid 10 tw6 th2 Pulse duration, RD high time tpd4 td4 Propagation delay time, BUSY falling edge to next RD (or CS for read cycle) falling edge tsu3 th3 Setup time, BYTE or BUS18/16 rising edge to RD falling edge Hold time, BYTE or BUS18/16 falling edge to RD falling edge 10 tdis Disable time, RD High (CS high for read cycle) to 3-stated data bus 30 ns td5 Delay time, BUSY low to MSB data valid delay time 40 ns 30 µs Pulse duration, BUSY signal high Setup time, RD high to CS high 40 ns 0 ns 0 ns 50 ns Enable time, RD low (or CS low for read cycle) to data valid Hold time, last RD (or CS for read cycle ) rising edge to CONVST falling edge Delay time, BYTE edge to BUS18/16 edge skew 30 ns ns 30 ns 20 ns 125 ns Max(td5) ns 0 ns 10 ns tsu4 Setup time, BYTE or BUS18/16 change before BUSY falling edge 10 (1) All input signals are specified with tr = tf = 5 ns (10% to 90% of +VBD) and timed from a voltage level of (VIL + VIH)/2. (2) See timing diagrams. (3) All timing are measured with 10 pF equivalent loads on all data bits and BUSY pins. ns 7 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 PIN ASSIGNMENTS BUSY DB0 DB1 DB2 DB3 DB4 DB5 DB6 DB7 DB8 DB9 BDGND PFB PACKAGE (TOP VIEW) 36 35 34 33 32 31 30 29 28 27 26 25 37 24 38 23 39 22 40 21 41 20 42 19 43 18 44 17 45 16 46 15 47 14 48 3 4 5 6 7 8 13 9 10 11 12 REFIN BIAS NC +VA AGND +IN –IN AGND +VA +VA 1 2 NC – No connection. 8 AGND AGND +VBD BUS18/16 BYTE CONVST RD CS +VA AGND AGND +VA REFM REFM +VBD DB10 DB11 DB12 DB13 DB14 DB15 DB16 DB17 AGND AGND +VA ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 TERMINAL FUNCTIONS NAME NO. I/O 5, 8, 11, 12, 14, 15, 44, 45 – Analog ground BDGND 25 – Digital ground for bus interface digital supply BIAS 2 I Bias to internal circuit BUSY 36 O Status output. High when a conversion is in progress. BUS18/16 38 I Bus size select input. Used for selecting 18-bit or 16-bit wide bus transfer. 0: Data bits output on the 18-bit data bus pins DB[17:0]. 1: Last two data bits D[1:0] from 18-bit wide bus output on: a) the low byte pins DB[9:2] if BYTE = 0 b) the high byte pins DB[17:10] if BYTE = 1 BYTE 39 I Byte select input. Used for 8-bit bus reading. 0: No fold back 1: Low byte D[9:2] of the 16 most significant bits is folded back to high byte of the 16 most significant pins DB[17:10]. CONVST 40 I Convert start CS 42 I Chip select AGND DESCRIPTION 8-Bit Bus BYTE = 0 Data Bus BYTE = 1 16-Bit Bus BYTE = 1 BYTE = 0 BYTE = 0 18-Bit Bus BYTE = 0 BUS18/16 = 0 BUS18/16 = 0 BUS18/16 = 1 BUS18/16 = 0 BUS18/16 = 1 BUS18/16 = 0 DB17 16 O D17 (MSB) D9 All ones D17 (MSB) All ones D17 (MSB) DB16 17 O D16 D8 All ones D16 All ones D16 DB15 18 O D15 D7 All ones D15 All ones D15 DB14 19 O D14 D6 All ones D14 All ones D14 DB13 20 O D13 D5 All ones D13 All ones D13 DB12 21 O D12 D4 All ones D12 All ones D12 DB11 22 O D11 D3 D1 D11 All ones D11 DB10 23 O D10 D2 D0(LSB) D10 All ones D10 DB9 26 O D9 All ones All ones D9 All ones D9 DB8 27 O D8 All ones All ones D8 All ones D8 DB7 28 O D7 All ones All ones D7 All ones D7 DB6 29 O D6 All ones All ones D6 All ones D6 DB5 30 O D5 All ones All ones D5 All ones D5 DB4 31 O D4 All ones All ones D4 All ones D4 DB3 32 O D3 All ones All ones D3 D1 D3 DB2 33 O D2 All ones All ones D2 D0 (LSB) D2 DB1 34 O D1 All ones All ones D1 All ones D1 DB0 35 O D0 (LSB) All ones All ones D0 (LSB) All ones D0 (LSB) –IN 7 I Inverting input channel +IN 6 I Noninverting input channel NC 3 – No connection REFIN 1 I Reference input. REFM 47, 48 I Reference ground. RD 41 I Synchronization pulse for the parallel output. +VA 4, 9, 10, 13, 43, 46 – Analog power supplies, 5-V dc 24, 37 – Digital power supply for bus +VBD 9 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 TIMING DIAGRAMS tw2 tw1 CONVST tpd1 tpd2 tw4 tw3 BUSY tsu1 CS CONVERT† t(CONV) t(CONV) SAMPLING† (When CS Toggle) t(ACQ) BYTE th1 BUS 18/16 tsu2 tpd4 th2 td1 RD tdis ten DB[17:12] Hi–Z MSB Hi–Z D[17:12] D[9:4] DB[11:10] Hi–Z Hi–Z D[11:10] D[3:2] D[1:0] DB[9:0] Hi–Z Hi–Z D[9:0] †Signal internal to device Figure 1. Timing for Conversion and Acquisition Cycles With CS and RD Toggling 10 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 tw1 tw2 CONVST tpd1 tpd2 tw4 tw3 BUSY tsu1 CS CONVERT† t(CONV) t(CONV) SAMPLING† (When CS Toggle) t(ACQ) BYTE th1 BUS 18/16 tpd4 th2 RD = 0 ten DB[17:12] Hi–Z tdis MSB Hi–Z D[17:12] D[9:4] DB[11:10] Hi–Z Hi–Z D[11:10] D[3:2] D[1:0] DB[9:0] Hi–Z Hi–Z D[9:0] †Signal internal to device NOTE: RD cannot be tied to BDGND. Three read cycles are required at power on. Figure 2. Timing for Conversion and Acquisition Cycles With CS Toggling, RD Held at BDGND After Power-On Initialization 11 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 tw1 tw2 CONVST tpd1 tpd2 tw4 tw3 BUSY CS = 0 CONVERT† t(CONV) t(CONV) t(ACQ) SAMPLING† (When CS = 0) BYTE th1 BUS 18/16 tpd4 th2 RD tdis ten DB[17:12] Hi–Z MSB Hi–Z D[17:12] D[9:4] DB[11:10] Hi–Z Hi–Z D[11:10] D[3:2] D[1:0] DB[9:0] Hi–Z Hi–Z D[9:0] †Signal internal to device Figure 3. Timing for Conversion and Acquisition Cycles With CS Tied to BDGND, RD Toggling 12 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 tw2 tw1 CONVST tpd1 tpd2 tw4 tw3 BUSY CS = 0 CONVERT† t(CONV) t(CONV) t(ACQ) SAMPLING† (When CS = 0) BYTE BUS 18/16 RD = 0 th1 th1 td5 D[9:4] DB[17:12] Next D[17:12] D[17:12] DB[11:10] D[11:10] D[3:2] D[1:0] Next D[11:10] DB[9:0] D[9:0] Next D[9:0] †Signal internal to device NOTE: RD cannot be tied to BDGND. Three read cycles are required at power on. Figure 4. Timing for Conversion and Acquisition Cycles With CS and RD Held at BDGND After Power-On Initialization - Auto Read 13 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 CS RD BYTE BUS 18/16 ten ten DB[17:0] Hi–Z tdis Valid Hi–Z td3 tdis td3 Valid Valid Figure 5. Detailed Timing for Read Cycles 14 Hi–Z ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 TYPICAL CHARACTERISTICS† SIGNAL-TO-NOISE RATIO vs FREE-AIR TEMPERATURE HISTOGRAM (DC Code Spread) HALF SCALE 131071 CONVERSIONS 18000 87.9 +VA = 5 V, +VBD = 3 V Code = 131046 14000 12000 10000 8000 6000 4000 87.7 87.6 87.5 87.4 87.3 2000 87.2 –40 131064 131046 0 131027 +VA = 5 V, +VBD = 3 V 87.8 SNR – Signal-to-Noise Ratio – dB 16000 –25 SIGNAL-TO-NOISE + DISTORTION vs FREE-AIR TEMPERATURE SPURIOUS FREE DYNAMIC RANGE vs FREE-AIR TEMPERATURE 87.9 116 +VA = 5 V, +VBD = 3 V 87.8 SFDR – Spurious Free Dynamic Range – dB SINAD– Signal-To-Noise + Distortion – dB 80 Figure 7 Figure 6 87.7 87.6 87.5 87.4 87.3 87.2 –40 –10 5 20 35 50 65 TA – Free-Air Temperature – °C –25 –10 5 20 35 50 65 TA – Free-Air Temperature – °C Figure 8 80 +VA = 5 V, +VBD = 3 V 115 114 113 112 111 110 109 108 107 106 –40 –25 –10 5 20 35 50 65 TA – Free-Air Temperature – °C 80 Figure 9 † At –40°C to 85°C, +VA = 5 V, +VBD = 5 V, REFIN = 4.096 V and fsample = 500 kHz (unless otherwise noted) 15 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 EFFECTIVE NUMBER OF BITS vs FREE-AIR TEMPERATURE TOTAL HARMONIC DISTORTION vs FREE-AIR TEMPERATURE 14.31 +VA = 5 V, +VBD = 3 V –105 ENOB – Effective Number of Bits – Bits THD – Total Harmonic Distortion – dB –104 –106 –107 –108 –109 –110 –111 –40 14.29 14.28 14.27 14.26 14.25 14.24 14.23 14.22 14.21 –25 –10 5 20 35 50 65 TA – Free-Air Temperature – °C 14.20 –40 80 –25 –10 5 20 35 50 65 TA – Free-Air Temperature – °C SIGNAL-TO-NOISE RATIO vs INPUT FREQUENCY SIGNAL-TO-NOISE + DISTORTION vs INPUT FREQUENCY 87.26 89.0 87.25 87.24 SINAD– Signal-To-Noise + Distortion – dB +VA = 5 V, +VBD = 3 V 87.23 87.22 87.21 87.20 87.19 87.18 87.17 87.16 87.15 0 20 40 60 fi – Input Frequency – kHz Figure 12 80 100 +VA = 5 V, +VBD = 3 V 88.5 88.0 87.5 87.0 86.5 86.0 85.5 85.0 0 20 40 60 80 fi – Input Frequency – kHz Figure 13 † At –40°C to 85°C, +VA = 5 V, +VBD = 5 V, REFIN = 4.096 V and fsample = 500 kHz (unless otherwise noted) 16 80 Figure 11 Figure 10 SNR – Signal-to-Noise Ratio – dB +VA = 5 V, +VBD = 3 V 14.30 100 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 SPURIOUS FREE DYNAMIC RANGE vs INPUT FREQUENCY EFFECTIVE NUMBER OF BITS vs INPUT FREQUENCY 120 +VA = 5 V, +VBD = 3 V 14.20 ENOB – Effective Number of Bits – Bits SFDR – Spurious Free Dynamic Range – dB 14.25 14.15 14.10 14.05 14.00 13.95 13.90 +VA = 5 V, +VBD = 3 V 115 110 105 100 95 90 13.85 0 20 40 60 fi – Input Frequency – kHz 80 0 100 40 60 80 fi – Input Frequency – kHz 100 Figure 15 Figure 14 TOTAL HARMONIC DISTORTION vs INPUT FREQUENCY SUPPLY CURRENT vs SAMPLE RATE –80 19 +VA = 5 V, +VBD = 3 V –85 +VA = 5 V, Current of +VA only 18 –90 Supply Current – mA THD – Total Harmonic Distortion – dB 20 –95 –100 –105 17 16 15 –110 –115 0 20 40 60 80 fi – Input Frequency – kHZ Figure 16 100 14 125 250 375 Sample Rate – KSPS 500 Figure 17 † At –40°C to 85°C, +VA = 5 V, +VBD = 5 V, REFIN = 4.096 V and fsample = 500 kHz (unless otherwise noted) 17 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 INTEGRAL NONLINEARITY vs SAMPLE RATE DIFFERENTIAL NONLINEARITY vs SAMPLE RATE 3.0 1.50 2.5 1.25 1.5 DNL – Differential Nonlinearity – LSB INL – Integral Nonlinearity – LSB 2.0 Max 1.0 0.5 +VA = 5 V, TA = 25 °C 0.0 –0.5 –1.0 –1.5 –2.0 –2.5 Min –3.0 +VA = 5 V, TA = 25 °C 0.75 0.50 0.25 0.00 –0.25 –0.50 Min –0.75 –3.5 –4.0 125 Max 1.00 200 275 350 425 Sample Rate – KSPS –1.00 125 500 Figure 18 200 275 350 425 Sample Rate – KSPS 500 Figure 19 OFFSET VOLTAGE vs SUPPLY VOLTAGE GAIN ERROR vs SUPPLY VOLTAGE –0.30 0 –0.32 TA = 25 °C –2 –0.002 Offset Voltage – mV Gain Error – %FS –0.34 –0.004 –4 –0.006 –6 –0.008 –8 –0.36 –0.38 –0.40 –0.42 –0.44 –0.010 –10 –0.46 –0.012 –12 4.75 5.00 +VA – Supply Voltage – V Figure 20 5.25 –0.48 4.75 5.00 +VA – Supply Voltage – V Figure 21 † At –40°C to 85°C, +VA = 5 V, +VBD = 5 V, REFIN = 4.096 V and fsample = 500 kHz (unless otherwise noted) 18 5.25 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 GAIN ERROR vs FREE-AIR TEMPERATURE SUPPLY CURRENT vs SUPPLY VOLTAGE –0.01 20.0 TA = 25 °C, Current of +VA only 19.5 19.0 Gain Error – %FS Supply Current – mA Vref = 4.1 V 18.5 18.0 –0.02 Vref = 2.5 V 17.5 17.0 4.75 5.00 +VA – Supply Voltage – V –0.03 –40 5.25 –20 0 20 40 60 80 TA – Free-Air Temperature – °C Figure 23 Figure 22 OFFSET VOLTAGE vs TEMPERATURE SUPPLY CURRENT vs FREE-AIR TEMPERATURE –0.20 18.14 Vref = 4.096 V +VA = 5 V, TA = 25 °C –0.22 +VA = 5 V 18.12 Supply Current – mA Offset Voltage – mV 18.10 –0.24 –0.26 –0.28 18.08 18.06 18.04 18.02 18.00 –0.30 Vref = 2.5 V –0.32 –40 –25 –10 5 20 35 50 TA – Temperature – °C Figure 24 17.98 65 80 17.96 –40 –20 0 20 40 60 TA – Temperature – °C 80 Figure 25 † At –40°C to 85°C, +VA = 5 V, +VBD = 5 V, REFIN = 4.096 V and fsample = 500 kHz (unless otherwise noted) 19 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 DIFFERENTIAL NONLINEARITY (Min) vs TEMPERATURE DIFFERENTIAL NONLINEARITY (Max) vs TEMPERATURE –0.60 1.7 DNL – Differential Nonlinearity (min) – LSB DNL – Differential Nonlinearity (max) – LSB 1.8 +VA = 5 V, TA = 25 °C Max 1.6 1.5 1.4 1.3 1.2 –40 –25 –10 5 20 35 50 TA – Temperature – °C 65 –0.65 –0.70 –0.75 –0.80 Min –0.85 –0.90 –0.95 –1.00 –40 80 +VA = 5 V, TA = 25 °C –25 INTEGRAL NONLINEARITY (Max) vs TEMPERATURE +VA = 5 V, TA = 25 °C INL – Integral Nonlinearity (min) – LSB INL – Integral Nonlinearity (max) – LSB –2.0 Max 3.5 3.0 2.5 –25 –10 5 20 35 50 TA – Temperature – °C Figure 28 65 80 –2.2 +VA = 5 V, TA = 25 °C –2.4 –2.6 –2.8 Min –3.0 –3.2 –3.4 –3.6 –40 –25 –10 5 20 35 50 TA – Temperature – °C Figure 29 † At –40°C to 85°C, +VA = 5 V, +VBD = 5 V, REFIN = 4.096 V and fsample = 500 kHz (unless otherwise noted) 20 80 INTEGRAL NONLINEARITY (Min) vs TEMPERATURE 4.5 2.0 –40 65 Figure 27 Figure 26 4.0 –10 5 20 35 50 TA – Temperature – °C 65 80 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 OFFSET VOLTAGE vs REFERENCE VOLTAGE INTEGRAL NONLINEARITY vs REFERENCE VOLTAGE –0.20 5 –0.22 Max 3 –0.24 2 Offset Voltage – mV INL – Integral Nonlinearity – LSB 4 1 +VA = 5 V 0 –1 –2 Min +VA = 5 V, TA = 25 °C –0.26 –0.28 –0.30 –0.32 –0.34 –3 –0.36 –4 –0.38 –5 –6 2.0 2.5 3.0 3.5 4.0 –0.40 2.5 4.5 Vref – Reference Voltage – V Figure 30 3.0 3.5 Vref – Reference Voltage – V 4.0 Figure 31 DIFFERENTIAL NONLINEARITY vs REFERENCE VOLTAGE 5 DNL – Differential Nonlinearity – LSB +VA = 5 V 4 Max 3 2 1 0 Min –1 –2 2.0 2.5 3.0 3.5 4.0 Vref – Reference Voltage – V 4.5 Figure 32 † At –40°C to 85°C, +VA = 5 V, +VBD = 5 V, REFIN = 4.096 V and fsample = 500 kHz (unless otherwise noted) 21 ADS8383 www.ti.com DNL – Differential Linearity Error – LSBs SLAS005B – DECEMBER 2002 – REVISED MAY 2003 DIFFERENTIAL LINEARITY ERROR vs CODE 3 2.5 2 1.5 1 0.5 0 –0.5 –1 –1.5 –2 –2.5 –3 0 65536 196605 131072 262144 Code Figure 33 INL – Integral Linearity Error – LSBs INTEGRAL LINEARITY ERROR vs CODE 7 5 3 1 –1 –3 –5 –7 0 65536 131072 196608 262144 Code Figure 34 FFT SPECTRAL RESPONSE (100 kHz Input) 0 –20 16384 Points, fs = 500 kHz, (+IN – –IN) = 4 VP-P Amplitude – dB –40 –60 –80 –100 –120 –140 –160 –180 0 50000 100000 150000 200000 f – Frequency – Hz Figure 35 † At –40°C to 85°C, +VA = 5 V, +VBD = 5 V, REFIN = 4.096 V and fsample = 500 kHz (unless otherwise noted) 22 250000 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 FFT SPECTRAL RESPONSE (50 kHz Input) 0 –20 Amplitude – dB –40 16384 Points, fs = 500 kHz, (+IN – –IN) = 4 VP-P –60 –80 –100 –120 –140 –160 –180 0 50000 100000 150000 200000 250000 f – Frequency – Hz Figure 36 † At –40°C to 85°C, +VA = 5 V, +VBD = 5 V, REFIN = 4.096 V and fsample = 500 kHz (unless otherwise noted) 23 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 APPLICATION INFORMATION MICROCONTROLLER INTERFACING ADS8383 to 8-Bit Microcontroller Interface Figure 37 shows a parallel interface between the ADS8383 and a typical microcontroller using the 8-bit data bus. The BUSY signal is used as a falling-edge interrupt to the microprocessor. Analog 5 V 0.1 µF AGND 10 µF Ext Ref Input 0.1 µF Micro Controller GPIO GPIO GPIO GPIO RD AD[7:0] –IN +IN +VA REFIN REFM AGND Analog Input Ext Bias Voltage BIAS 1 µF Digital 3 V Data Bus D[17:0] CS AD8383 BYTE BUS18/16 CONVST RD DB[17:10] AGND 0.1 µF BDGND BDGND +VBD Figure 37. ADS8383 Application Circuitry 24 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 PRINCIPLES OF OPERATION The ADS8383 is a high-speed successive approximation register (SAR) analog-to-digital converter (ADC). The architecture is based on charge redistribution which inherently includes a sample/hold function. See Figure 37 for the application circuit for the ADS8383. The conversion clock is generated internally. The conversion time of 1.6 µs is capable of sustaining a 500-kHz throughput. The analog input is provided to two input pins: +IN and –IN. When a conversion is initiated, the differential input on these pins is sampled on the internal capacitor array. While a conversion is in progress, both inputs are disconnected from any internal function. REFERENCE The ADS8383 can operate with an external 4.096-V reference for a corresponding full-scale range of 4.096 V. BIASING THE ADS8383 The ADS8383 requires an external 2.048-V bandgap reference to generate the bias currents for internal circuitry. Figure 38 shows the internal circuitry used to generate the bias currents. The bias generation circuit also pumps 100 µA (150 µA max) out from the BIAS pin. The bandgap used should be capable of sinking 100 µA (150 µA max) while holding the voltage on the pin steady. Table 1 shows the specification of the bandgap used to drive the BIAS pin of the ADS8383. 5V +VA ADS8383 100 µA BIAS_INT BIAS AGND Figure 38. Bias Current Generation Table 1. Bias Specifications PARAMETER MIN TYP Output Voltage 2 2.048 2.1 V 100 150 µA Isink MAX UNITS Any common bandgap like REF3020 can be used to drive the BIAS pin of the ADS8383. Figure 39 shows how REF3020 can be used with the ADS8383. A 1 µF decoupling capacitor is recommended between pins 2 and AGND of the ADS8383 for optimal performance. 5V 1 0.47 µF 50 Ω REF3020 2 3 2 22 µF ADS8383 AGND AGND Figure 39. Using the REF3020 to Drive the ADS8383 BIAS Pin 25 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 ANALOG INPUT When the converter enters the hold mode, the voltage difference between the +IN and –IN inputs is captured on the internal capacitor array. The voltage on the –IN input is limited between –0.2 V and 0.2 V, allowing the input to reject small signals which are common to both the +IN and –IN inputs. The +IN input has a range of –0.2 V to Vref + 0.2 V. The input span (+IN – (–IN)) is limited to 0 V to Vref. The input current on the analog inputs depends upon a number of factors: sample rate, input voltage, and source impedance. Essentially, the current into the ADS8383 charges the internal capacitor array during the sample period. After this capacitance has been fully charged, there is no further input current. The source of the analog input voltage must be able to charge the input capacitance (45 pF) to an 18-bit settling level within the acquisition time (400 ns) of the device. When the converter goes into the hold mode, the input impedance is greater than 1 GΩ. Care must be taken regarding the absolute analog input voltage. To maintain the linearity of the converter, the +IN and –IN inputs and the span (+IN – (–IN)) should be within the limits specified. Outside of these ranges, the converter’s linearity may not meet specifications. To minimize noise, low bandwidth input signals with low-pass filters should be used. Care should be taken to ensure that the output impedance of the sources driving the +IN and –IN inputs are matched. If this is not observed, the two inputs could have different setting times. This may result in offset error, gain error, and linearity error which changes with temperature and input voltage. DIGITAL INTERFACE Timing And Control See the timing diagrams in the specifications section for detailed information on timing signals and their requirements. The ADS8383 uses an internal oscillator generated clock which controls the conversion rate and in turn the throughput of the converter. No external clock input is required. Conversions are initiated by bringing the CONVST pin low for a minimum of 20 ns (after the 20 ns minimum requirement has been met, the CONVST pin can be brought high), while CS is low. The ADS8383 switches from the sample to the hold mode on the falling edge of the CONVST command. A clean and low jitter falling edge of this signal is important to the performance of the converter. The BUSY output is brought high immediately following CONVST going low. BUSY stays high through the conversion process and returns low when the conversion has ended. Sampling starts with the falling edge of the BUSY signal when CS is tied low or starts with the falling edge of CS when BUSY is low. Both RD and CS can be high during and before a conversion with one exception (CS must be low when CONVST goes low to initiate a conversion). Both the RD and CS pins are brought low in order to enable the parallel output bus with the conversion. Reading Data The ADS8383 outputs full parallel data in straight binary format as shown in Table 2. The parallel output is active when CS and RD are both low. There is a minimal quiet zone requirement around the falling edge of CONVST. This is 125 ns prior to the falling edge of CONVST and 40 ns after the falling edge. No data read should be attempted within this zone. Any other combination of CS and RD sets the parallel output to 3-state. BYTE and BUS18/16 are used for multiword read operations. BYTE is used whenever lower bits on the bus are output on the higher byte of the bus. BUS18/16 is used whenever the last two bits on the 18-bit bus is output on either bytes of the higher 16-bit bus. Refer to Table 2 for ideal output codes. 26 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 Table 2. Ideal Input Voltages and Output Codes DESCRIPTION ANALOG VALUE FULL SCALE RANGE Vref Vref/262144 Least significant bit (LSB) Full scale Midscale Midscale – 1 LSB Zero DIGITAL OUTPUT STRAIGHT BINARY BINARY CODE HEX CODE Vref – 1 LSB Vref/2 11 1111 1111 1111 1111 3FFFF 10 0000 0000 0000 0000 20000 Vref/2 – 1 LSB 0V 01 1111 1111 1111 1111 1FFFF 00 0000 0000 0000 0000 00000 The output data is a full 18-bit word (D17–D0) on DB17–DB0 pins (MSB–LSB) if both BUS18/16 and BYTE are low. The result may also be read on a 16-bit bus by using only pins DB17–DB2. In this case two reads are necessary: the first as before, leaving both BUS18/16 and BYTE low and reading the 16 most significant bits (D17–D2) on pins DB17–DB2, then bringing BUS18/16 high while holding BYTE low. When BUS18/16 is high, the lower two bits (D1–D0) appear on pins DB3–DB2. The result may also be read on an 8-bit bus for convenience. This is done by using only pins DB17–DB10. In this case three reads are necessary: the first as before, leaving both BUS18/16 and BYTE low and reading the 8 most significant bits on pins DB17–DB10, then bringing BYTE high while holding BUS18/16 low. When BYTE is high, the medium bits (D9–D2) appear on pins DB17–DB10. The last read is done by bringing BUS18/16 high while holding BYTE high. When BUS18/16 is high, the lower two bits (D1–D0) appear on pins DB11–DB10. The last read cycle is not necessary if only the first 16 most significant bits are of interest. All of these multiword read operations can be performed with multiple active RD (toggling) or with RD held low for simplicity. This is referred to as the AUTO READ operation. Note that RD may not be tied to BDGND permanently due to the requirement of power-on initialization. Table 3. Conversion Data Read Out DATA READ OUT BYTE BUS18/16 DB17–DB12 DB11–DB10 DB9–DB4 DB3–DB2 DB1–DB0 High High All One’s D1–D0 All One’s All One’s All One’s Low High All One’s All One’s All One’s D1–D0 All One’s High Low D9–D4 D3–D2 All One’s All One’s All One’s Low Low D17–D12 D11–D10 D9–D4 D3–D2 D1–D0 POWER-ON INITIALIZATION At first power on there are three read cycles required (RD must be toggled three times). If conversion cycle is attempted before these intialization read cycles, the first three conversion cycles will not produce valid results. This is used to load factory trimming data for a specific device to assure high accuracy of the converter. Because of this requirement, the RD pin cannot be tied permanently to BDGND. System designers can still achieve the AUTO READ function if the power-on requirement is satisfied. LAYOUT For optimum performance, care should be taken with the physical layout of the ADS8383 circuitry. As the ADS8383 offers single-supply operation, it will often be used in close proximity with digital logic, microcontrollers, microprocessors, and digital signal processors. The more digital logic present in the design and the higher the switching speed, the more difficult it is to achieve good performance from the converter. The basic SAR architecture is sensitive to glitches or sudden changes on the power supply, reference, ground connections and digital inputs that occur just prior to latching the output of the analog comparator. Thus, driving any single conversion for an n-bit SAR converter, there are at least n windows in which large external transient voltages can affect the conversion result. Such glitches might originate from switching power supplies, nearby digital logic, or high power devices. The degree of error in the digital output depends on the reference voltage, layout, and the exact timing of the external event. 27 ADS8383 www.ti.com SLAS005B – DECEMBER 2002 – REVISED MAY 2003 On average, the ADS8383 draws very little current from an external reference as the reference voltage is internally buffered. If the reference voltage is external and originates from an op amp, make sure that it can drive the bypass capacitor or capacitors without oscillation. A 0.1-µF bypass capacitor is recommended from pin 1 (REFIN) directly to pin 48 (REFM). REFM and AGND should be shorted on the same ground plane under the device. The AGND and BDGND pins should be connected to a clean ground point. In all cases, this should be the analog ground. Avoid connections which are too close to the grounding point of a microcontroller or digital signal processor. If required, run a ground trace directly from the converter to the power supply entry point. The ideal layout consists of an analog ground plane dedicated to the converter and associated analog circuitry. As with the AGND connections, +VA should be connected to a 5-V power supply plane or trace that is separate from the connection for digital logic until they are connected at the power entry point. Power to the ADS8383 should be clean and well bypassed. A 0.1-µF ceramic bypass capacitor should be placed as close to the device as possible. See Table 4 for the placement of the capacitor. In addition, a 1-µF to 10-µF capacitor is recommended. In some situations, additional bypassing may be required, such as a 100-µF electrolytic capacitor or even a Pi filter made up of inductors and capacitors—all designed to essentially low-pass filter the 5-V supply, removing the high frequency noise. Table 4. Power Supply Decoupling Capacitor Placement POWER SUPPLY PLANE SUPPLY PINS CONVERTER ANALOG SIDE CONVERTER DIGITAL SIDE Pin pairs that require shortest path to decoupling capacitors (4,5), (8,9), (10,11), (13,15), (43,44), (45,46) (24,25) Pins that require no decoupling 12, 14 37 28 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using TI components. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information published by TI regarding third–party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for such altered documentation. Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. Mailing Address: Texas Instruments Post Office Box 655303 Dallas, Texas 75265 Copyright 2003, Texas Instruments Incorporated